In the context of IPv6 addresses on MikroTik devices (and in general), “link-local” and “global” addresses refer to two types of scope that IP addresses can have. Each of these types fulfills specific functions within a network.

Below, we explain the main differences between the two:

Link-Local Addresses

• Scope and Use: Link-local addresses have a scope limited to a single link or network segment. This means that they are valid and unique only within the local network or subnet and are not routable beyond that link. In practice, this means that link-local addresses are used for communication between devices on the same physical network or subnet without needing to go through a router.
• Autoconfiguration: Link-local addresses are automatically generated for each network interface that uses IPv6, allowing devices to communicate with each other on the same network without the need for manual configuration or DHCP. This autoconfiguration is a key feature of IPv6.
• Prefix: Link-local addresses always begin with the prefix fe80::/10.
• Usage Example: They are used for the initial configuration of a device, discovery of neighbors, and for certain control protocols such as ICMPv6.

Global Unicast Addresses

• Scope and Use: Global unicast addresses have global reach, meaning they are designed to be used on the Internet and can be routed across multiple networks. These addresses are equivalent to public IPv4 addresses and allow communication over the Internet.
• Assignment: Unlike link-local addresses, global unicast addresses must be assigned by a network administrator or automatically through DHCPv6. These addresses are provided by an Internet Service Provider (ISP) or a regional Internet registry.
• Prefix: The prefixes for global unicast addresses vary, but do not begin with fe80::. A common example of a global unicast prefix is 2001::/3.
• Usage Example: They are used for communications on the Internet, allowing devices to be globally accessible or communicate beyond their local network.

Conclusion

The main difference between link-local and global unicast in IPv6 lies in its scope and use. Link-local addresses are restricted to a single link or subnet for local communications, while global unicast addresses can be used for communications over the Internet.

Both types of addresses are essential for the operation of IPv6 networks, facilitating both automatic local communication and global connectivity.